The literature reference referred to above describes a triggering arrangement for a passenger restraint system which, selectively, may be either a seat-and-lapbelt or other belt tensioning device, or, for example, an airbag. The literature describes such a system in which an accelerometer, or, more accurately, a deceleration sensor, senses deceleration of the vehicle of a magnitude representative of a collision or an impending collision, and provides an output signal to an evaluation circuit. The output signal then provides a triggering or firing signal to an electrical firing circuit which, for example by means of an explosive pellet or similar chemical reaction, causes immediate inflation of an airbag, or locking and/or tightening of a belting arrangement. The electrical portion of the system operates practically instantaneously; the chemical portion can operate later, and the separation between electrical operation and other operation is provided since, in case of a collision, electrical power may be interrupted by destruction of the electrical battery in the vehicle, or conductors and wires connected thereto.
The signal levels supplied by the accelerometer, and processed within the evaluation circuit may be very low. It has previously been proposed--see U.S. Pat. No. 4,164,263, Heintz et al (to which German Patent Disclosure Document DE-OS No. 26 55 604 corresponds)--to locate the electrical portion of the evaluation circuit, including, if desired, the accelerometer in a separate restraint housing. This housing must be made specially, and introducing the respective elements therein is an expensive manufacturing and assembly operation, particularly since the accelerometer itself must be secured in a separate accelerometer housing or in a partial housing structure within the overall restraint housing element.